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Rretrnfl5oclockthicknessoct

Published: August 9, 2026Updated: August 17, 2026

A non-invasive eye imaging test that measures the thickness of the retinal nerve fiber layer in the right eye to assess optic nerve health.

Quick summary

{"Uses OCT technology to capture detailed cross-sectional images of the retina","Measures RNFL thickness at specific locations (clock hour 5) in the right eye","Helps detect and monitor glaucoma and other optic nerve conditions","The test is quick, painless, and does not require any blood samples","Results are compared to normal ranges to identify abnormalities"}

Medically reviewed by WellAlly Editorial TeamLast reviewed August 17, 2026Editorial policy

Key facts at a glance

LOINC
86309-2
Short code
RNFL-R5-OCT
Synonyms
R ret RNFL 5 o'clock thickness OCT
Category
cardiac
Sample
serum
Container
Not applicable - imaging procedure
Units
N/A
Ref low
50
Ref high
80
Critical range
— – 10000 N/A
Fasting
false
Population
adult
Sex
all
Age range
18–100 years
Method
Optical Coherence Tomography (OCT)
CPT
92134
SNOMED
399555008
Specimen volume
Not applicable - imaging procedure
Stability
Not applicable - imaging procedure
Hemolysis max
500
Lipemia max
1000
Icterus max
500
TAT
1–24 hours
Order
routine

What is this test?

The Right Retina Retinal Nerve Fiber Layer (RNFL) Thickness Test is an eye imaging procedure that uses Optical Coherence Tomography (OCT) to measure the thickness of the retinal nerve fiber layer in your right eye. Specifically, it measures the RNFL thickness at clock hour 5, which corresponds to a specific location on the optic nerve head.

How is the test performed?

During the test, you will sit in front of an OCT machine. You will be asked to place your chin on a support and look at a fixed target. The machine will then scan your right eye using light waves to create detailed cross-sectional images of your retina and optic nerve. The entire procedure typically takes only a few minutes and is completely painless. No eye drops, blood samples, or radiation are involved.

Why is RNFL thickness important?

The retinal nerve fiber layer consists of nerve fibers that carry visual information from the retina to the brain. Measuring its thickness helps doctors assess the health of your optic nerve. Thinning of the RNFL can indicate damage to the optic nerve, which may be caused by conditions such as glaucoma, optic neuritis, or other neurodegenerative diseases.

What should I expect after the test?

After the scan, your doctor will analyze the images and compare your RNFL thickness measurements to normal reference values. The results are usually presented in a color-coded map showing which areas have normal, thinning, or abnormally thick nerve fiber layers. Your doctor will discuss the findings with you and recommend appropriate follow-up care if needed.

Reference range

Normal RNFL thickness at clock hour 5 typically ranges from 50-80 microns in healthy adults; values below 50 microns may indicate possible glaucomatous damageN/A

Specimen: serum

Patient should remove contact lenses if applicable; pupillary dilation may be performed for better visualization; no fasting required

Clinical interpretation

How abnormal results are interpreted and what conditions they suggest.

◆Associated findings1

Frequently asked questions

Do I need to prepare for the test?
No special preparation is needed. You can eat and drink normally before the test. However, you should avoid wearing eye makeup on the day of the test as it may interfere with the imaging. If you wear contact lenses, you may be asked to remove them before the scan.
Is the test painful?
No, the OCT test is completely painless. You may feel a slight discomfort from keeping your eyes open, but there is no contact with your eye or any invasive procedure involved.
How long does the test take?
The actual scanning process takes only about 1-2 minutes per eye. Including the time for positioning and preparation, the entire visit typically lasts about 10-15 minutes.
Will I need to have this test again?
If abnormalities are detected, your doctor may recommend periodic follow-up scans to monitor changes in your RNFL thickness over time. The frequency depends on your specific condition and risk factors. For glaucoma patients, annual or semi-annual testing is common.
What do the results mean?
Your results will show RNFL thickness measurements compared to normal reference values. Thinning of the RNFL at clock hour 5 (or other locations) may indicate optic nerve damage. However, your doctor will interpret the results in context with your overall eye health, medical history, and other test findings.
  1. 1
    American Academy of Ophthalmology - OCT for GlaucomaSource
  2. 2
    National Eye Institute - GlaucomaSource
  3. 3
    All About Vision - OCT Eye TestSource

Click any link to access the full source. PubMed Central (PMC) links provide free full-text access.

This information is for educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment.

Medical Disclaimer

This content is for general informational and educational purposes only and is not a substitute for professional medical advice, diagnosis, or treatment. Always seek the guidance of a qualified healthcare provider with any questions you have about a medical condition, and never disregard professional medical advice or delay seeking it because of something you read here.

If you think you may have a medical emergency, call your local emergency number or go to the nearest emergency department immediately.

Medically reviewed by WellAlly Editorial Team Last reviewed August 17, 2026. · Read our editorial policy